The postdoctoral research training program in Endocrinology and Diabetes at the Massachusetts General Hospital provides intensive research experience in basic or clinical investigation, complemented by a didactic component appropriate to the training goals. The trainees are primarily M.D.'s and M.D./Ph.D.'s who desire a career in investigative endocrinology and academic medicine, as well as Ph.D.'s who want further research training. The trainees are selected from a large applicant pool on the basis of prior academic and/or research achievement and evidence of strong commitment to a career in biomedical investigation. The Program director (J. Avruch) and the Associate Director (J. Florez) are senior and mid-career Physician-Scientists respectively who govern in conjunction with a committee of experienced endocrine scientists (Habener, Kronenberg, Crowley, Freeman, Grinspoon and Klibanski). The faculty consists of 42 active, well-funded scientists, whose interests range broadly across the subdisciplines of endocrinology and from clinical, bedside investigation to molecular mechanisms. The trainees are supervised closely by a primary faculty mentor, and interact extensively with junior faculty, who often serve as secondary mentors. An extensive program of didactic sessions complements the research activity. The training period is 2-4 years but may include several years additional experience at junior faculty status, so as to permit consolidation of skills and maximal competitiveness for independent support. The productivity of past trainees during training has been very high overall, as judged by the number and quality of trainee publications. Twenty seven of 44 program graduates since 2004 supported by this award remain in academia and ten are in the biotechnology/pharmaceutical industry. Among the 27 in academia, 7 have an R01 or equivalent (R21, DP2, U01 site PI), six others have K series award, and three have KL2/Medical Research Investigator Training awards from the Harvard CTSA. The facilities at the MGH are extensive, including an Institutional Clinical Research Support Program and over 50,000 square feet of modern laboratories dedicated to endocrine training faculty. This training grant is the central stabilizing financial element in this program, and is critical in enabling M.D. trainees to achieve careers in biomedical investigation.